1. Field of the Invention
The present invention relates, in general, to a reparation of thermal contraction sleeve and, more particularly, to a method of producing thermal shrinkable sleeves while increasing the adhesive force between the fabric sheet and the matrix sheet of a fabric-matrix layered thermal shrinkable sleeve and improving the production yield of the sleeves.
2. Description of the Prior Art
As well known to those skilled in the art, a variety of sealing elements have been used for the protection of joints of communication cables or electric wires from environmental impact or contamination. An example of conventionally used sealing elements for such joints is a thermal shrinkable sleeve made of polymeric materials.
Korean Patent No. 48,450, owned by Raychem Corporation of USA, discloses a representative example of such conventional polymeric thermal shrinkable sleeves. The polymeric thermal shrinkable sleeve, disclosed in the above Korean patent, uses high density polyethylene as a polymeric material, and has a matrix sheet. The elastic fabric sheet, set within the matrix sheet, is made of cross-linked polyethylene exposed to a radiation of 4xcx9c40 Mrads, while the matrix sheet is made of cross-linked polyethylene exposed to a radiation of not higher than 10 Mrads.
The above polymeric thermal shrinkable sleeve is advantageous in that it has a high shrinkage and is free from an undesired breakage of the elastic fabric sheet or the matrix sheet during a contraction of the sleeve, and accomplishes a desired pressure sealing effect for the joints of cables or wires.
However, the above sleeve is problematic in that the adhesive force between the elastic fabric sheet and the matrix sheet is somewhat low, thus sometimes allowing an unexpected separation of the fabric sheet from the matrix sheet. In addition, the process of producing the above sleeves undesirably consumes time and increases the production cost of such sleeves. The unexpected separation of the elastic fabric sheet from the matrix sheet may be prevented by an application of an expensive adhesive to the junction between the two sheets. However, the application of such an expensive adhesive to the junction between the sheets increases the production cost of the polymeric thermal shrinkable sleeve and complicates the process of producing the sleeves. Such a complex sleeve production process increases the cost of the sleeve production system.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method of producing thermal shrinkable sleeves, which increases the adhesive force between the fabric sheet and the matrix sheet of a fabric-matrix layered thermal shrinkable sleeve.
Another object of the present invention is to provide a method of producing thermal shrinkable sleeves while improving the production yield of the sleeves.
A further object of the present invention is to provide a method of producing thermal shrinkable sleeves, which produces inexpensive thermal shrinkable sleeves while reducing the production loss.
In order to accomplish the above object, the present invention provides a method of producing a thermal shrinkable sleeve, comprising the steps of: a)exposing polyethylene fibers elongated by 850%xcx9c1,200% to a radiation of 2.5xcx9c3.5 Mrads, thus cross-linking the polyethylene fibers; b)exposing the first surface of a fabric sheet made of the polyethylene fibers to a voltage of 20,000xcx9c25,000 V while passing the fabric sheet over a plurality of rollers, thus modifying the first surface of the fabric sheet, and forming a first matrix sheet, melt-extruded at a temperature of 300xc2x0 C.xcx9c380xc2x0 C., on the modified first surface of the fabric sheet, and integrating the first matrix sheet with the modified surface of the fabric sheet by allowing the fabric sheet with the first matrix sheet to pass through the nip between a first elastic roller and a first cooling roller; c)processing the second surface of the fabric sheet through the same process as that of step xe2x80x9cbxe2x80x9d and integrating a second matrix sheet with the modified second surface of the fabric sheet, thus forming a fabric-matrix layered body; and d)exposing the matrix sheets of the fabric-matrix layered body to a radiation of 2.5xcx9c3.5 Mrads, thus cross-linking the matrix sheets.